Fix issue #248: Align multiline help messages

[fanurs]

This PR fixes #248 by aligning multiline help messages. A previous PR, #259, attempted to fix the issue, but it was not finalized due to unresolved clang-tidy issues. This PR builds upon the work done in PR #259 and addresses the outstanding issues.

The key changes in this PR include:

1. Using spaces instead of "\t" to separate argument names and help messages. This makes the spacing independent of the terminal's tab width settings and simplifies testing.
2. Adding a test case to verify that all help messages are properly aligned.

Additionally, while working on this issue, I noticed that the -DCMAKE_CXX_STANDARD=17 flag is required when using CMake to build the test. This flag is currently not documented in the README:

argparse/README.md

Lines 1153 to 1160 in 557948f

	# Build the tests
	mkdir build
	cd build
	cmake -DARGPARSE_BUILD_SAMPLES=on -DARGPARSE_BUILD_TESTS=on ..
	make
	# Run tests
	./test/tests